1. Technical Field
The present invention relates to a light emitting apparatus, a method of driving a light emitting apparatus, and an electronic apparatus.
2. Related Art
In a light emitting apparatus in which a driving transistor controls a driving current supplied to a light emitting device, there is a problem of errors in a characteristic of the driving transistor (difference from a target value or non-uniformity among pixels). JPA-2008-9198 and JP-A-2007-310311 discloses a technology for compensating for an error of a threshold voltage or a mobility of the driving transistor by setting a gate-source voltage of the driving transistor to a threshold voltage of the driving transistor and then changing to a voltage according to gradation.
FIG. 21 is a circuit diagram illustrating a configuration of a pixel circuit P0 disclosed in JP-A-2008-9198. In the initialization period, the transistors Tr2 and Tr3 are set to the ON state, so that the gate-source voltage of the driving transistor Tdr is initialized to |Vss1−Vss2|. In the compensation period, the transistor Tr3 is transitioned into the OFF state, and the transistor Tr4 is transitioned into the ON state, so that a current is flown from the power supply line to the driving transistor Tdr. Accordingly, the gate-source voltage of the driving transistor Tdr asymptotically approaches the threshold voltage VTH. In the writing period, the transistor Tr2 is transitioned into the OFF state, the transistor Tr1 is transitioned into the ON state, and the voltage of the data line S1 is set to a data voltage according to the designated gradation of the pixel circuit P0. Accordingly, the voltage of the gate of the driving transistor Tdr is set to a value according to the data voltage. Next, the current according to the data voltage is flown to the driving transistor Tdr, so that the voltage of the source thereof is increased. Accordingly, a mobility compensation operation through negative feedback is performed. In the light emitting period, the transistor Tr1 is transitioned into the OFF state, so that the gate of the driving transistor 3B is in an electrically floating state. At this time, the voltage across the capacitance device Cs is stored as the voltage of the end point of the writing period, and a current according to the voltage is flown to the driving transistor Tdr, so that the voltage of the source of the driving transistor Tdr is increased. Accordingly, the voltage of the gate of the driving transistor Tdr is increased in conjunction with the voltage of the source (bootstrap operation). In addition, if the voltage of the source exceeds a light emitting threshold value, an OLED device E is in a state where the device emits light.
However, in the technology disclosed in JPA-2008-9198, since a large number of signal lines and transistors are provided to perform an initialization or compensation operation, there is a problem in that the configuration is complicated. On the other hand, in JP-A-2007-310311, the data lines are also used as the signal lines for supplying signals used for the initialization or compensation operation, so that the number of the signal lines or the number of the transistors can be reduced in comparison with JP-A-2008-9198. FIG. 22 is a diagram illustrating a configuration of a pixel circuit P1 disclosed in JP-A-2007-310311. In JP-A-2007-310311, a time period (that is, one horizontal scan time period) in which a selection transistor 3A is set to an ON state is provided with an initialization period, a compensation period, and a writing period. In the initialization period, a voltage of the data line DTL101 is set to a reference voltage V0 and a voltage of the power supply line DSL101 is set to a voltage Vcc_L (<V0), so that a gate-source voltage of a driving transistor 3E is initialized. In the compensation period, the voltage of the data line DTL101 is maintained to the reference voltage V0 and the voltage of the power supply line DSL101 is set to a high voltage Vcc_H (>Vcc_L), so that the gate-source voltage of the driving transistor 3B is allowed to asymptotically approach a threshold voltage of the driving transistor 3B. In the writing period, the voltage of the power supply line DSL101 is maintained to the high voltage Vcc_H and the voltage of the data line DTL101 is set to a data voltage Vin according to the designated gradation of the pixel circuit P1, so that a current according to the data voltage Vin is flown to the driving transistor 3B, thereby compensating for the mobility. After the writing period, if the light emitting period starts, the selection transistor 3A is set to the OFF state, so that the source voltage of the driving transistor 3B is increased. If the source voltage exceeds the light emitting threshold value, an OLED device 3D is in the state where the OLED device 3D emits light.
However, in the technology disclosed in JPA-2007-310311, in the time period (one horizontal scan time period) in which the selection transistor 3A is set to the ON state, since the reference voltage V0 and the data voltage Vin are configured to be time-divisionally supplied to the data line DTL101, there is s a problem in that it is difficult to secure a sufficient time period for writing the data voltage in the one horizontal scan time period.